Buildings in which people work and live have systems that monitor and sustain the comfort level of the building environment. Such systems include heating, ventilation and air conditioning (HVAC) systems, lighting systems, as well as others. HVAC and lighting systems have existed, at least at some level, for thousands of years.
HVAC and lighting systems have become sophisticated, and are often able to maintain careful balances of humidity and temperature, as well as provide fresh air and adequate light within buildings. Suitable temperature, humidity, light and oxygen levels contribute to the indoor environmental quality of a building or work place. Good environmental quality can translate to better productivity and health of the occupants.
The majority of building control systems maintains the occupants comfort by simply maintaining space temperature, which is measured using a thermostat or temperature sensor located on a wall. Although there is a strong correlation between temperature and human comfort, a better comfort index can be measured when the temperature is combined with relative humidity.
Combined temperature and humidity level is a better measure of heat or thermal energy content in a room and it is that thermal energy that needs to be removed (i.e. cooled) or supplemented by more energy (i.e. heated) to maintain the occupants at a comfortable level. The combined temperature and humidity levels are often termed as the “heat index” by the meteorological media.
As yet, however, there has been limited application of the combined heat/humidity index in the building control or HVAC industry. Costs related to sensing both temperature and relative humidity on a comprehensive scale has hindered such applications.
There is a need, therefore, for a cost-effective solution for implementing comfort control in buildings that takes into account both relative humidity and temperature.